In many prior art systems of mixing gasses and liquids, a gas is introduced into a liquid whereupon the gas/liquid mixture is forced to flow downwardly as a helical current through an outer chamber of a contact tank to a lower end thereof, and then back up through a center tube that extends upwardly from a lower region of the contact tank to an outlet conduit at the upper end of the contact tank. In the system taught in U.S. Pat. No. 5,865,995, the gas is introduced into a stream of untreated liquid and then the mixture is introduced into the contact tank. Some of the gas/liquid mixture in the contact tank is re-circulated and new gas is introduced into the re-circulated mixture. Furthermore, new untreated liquid is introduced by itself into the upper end of the contact tank.
Furthermore, in some prior art systems a gas/liquid mixture is introduced into a lower portion of an outer chamber in such a way that it forms an upwardly flowing helical current in the outer chamber. A gas removal outlet is provided in an inner chamber defined by an inner housing, radially inwardly of and axially below a passageway at the top of the inner housing that connects the outer chamber with the inner chamber. A liquid outlet conduit is provided below a bottom wall of the inner housing. An outlet in the bottom wall of the inner housing connects the lower end of the inner chamber to the outlet conduit.
Additionally, in some prior art systems the lower portion of the outer housing is often formed to include an inlet chamber. The gas/liquid inlet conduit is directed to discharge into the inlet chamber at a tangent thereby producing the helical current and enabling efficient mixing of the distinct phases. Furthermore, the lower portion of the outer housing may also include an outlet conduit.
There is a need in the prior art systems for an improved apparatus for treating a liquid with a gas wherein the helical current provides for efficient mixing of the two phases and wherein the less efficiently mixed portions are withdrawn from the apparatus for recirculation and reintroduction thereto. Often the mixture of gas and liquid produced by prior art devices is not sufficiently homogeneous to produce efficacious results. The need for even mixing is particularly acute when the gas/liquid mixture is, for example, ozone gas mixed with water which is commonly used as a cleaning and sanitizing agent in a wide variety of industrial applications.